Let \({\bf s}_i \!\in \! \mbox{$\mathbb {C}$}^{N_u}\)  denote the symbols for \(N_u\)  users in cell \(i\)  and \({\bf W}_i\!=\!\left[{\bf w}_{i,1},\ldots ,{\bf w}_{i,N_c}\right] \!\in \! \mbox{$\mathbb {C}$}^{N_b \times N_u} \)  collects the associated precoders.
We define the precoded signals as \({\bf x}_i = {\bf W}_i{\bf s}_i\) .
Upon generating \({\bf x}_i\) , the signal is treated by the low-resolution DACs with \(b\)  quantization bits.
For analytic tractability, we adopt the AQNM [1]}, [2]} that delivers a linear approximation of the quantization process derived from assuming a scalar minimum-mean-squared-error (MMSE) quantizer.
Under the AQNM, the quantized signal is modeled as
\({\bf x}_{{\rm q},i} = \alpha {\bf x}_i + {\bf q}_i\) 
